LytA is involved in the evasion of complement- mediated immunity and invasive disease by a pneumolysin-independent mechanism

Abstract

Streptococcus pneumoniae is one of the major causes of invasive disease accounting for more deaths than any other vaccine-preventable bacterial infection. Recognition by the complement system is a vital event in the clearance of this important human pathogen. We show here that the main autolytic enzyme of the bacterium,the amidase LytA, avoid complement-mediated immunity by a complex mechanism of impaired activation and increased down-regulation. Moreover, we demonstrated that both ply and lytA mutants were attenuated in pneumonia and sepsis and the virulence of the double mutant was greatly impaired demonstrating that both proteins play an important role in the establishment of the pneumococcal invasive disease.